Here's an idea for another cool but useless tool for you budding programmers! Have you ever tried the Classic app Conan the Librarian? It's been around for yeeaars. Basically, it's just an app with five or six sounds that monitors the input levels of your microphone. When you reach certain levels, Conan says something appropriate. I got a big laugh out of it a few years back.
Anyone interested in making a port?
Note: I have no knowledge at all about CoreAudio or really anything audio-related, else I'd probably take a stab at it.